An oxygen-blocking oriented multifunctional solid–electrolyte interphase as a protective layer for a lithium metal anode in lithium–oxygen batteries

Abstract

For a period of time, the O₂ cathode has been the focus of research, while the study of lithium anodes and their interactions is quite rare in rechargeable lithium–oxygen (Li–O₂) batteries. Actually, the unstable interface between a Li metal anode and the electrolyte in the presence of O₂ will eventually lead to battery failure. It was proposed that lithium nitrate (LiNO₃), a well-known stabilizing additive being able to form a passivation solid–electrolyte interphase (SEI) on the Li metal surface, could be introduced into the electrolyte of Li–O₂ batteries to improve their performance. Nevertheless, the effective utilization of LiNO₃ in this system has heretofore been limited due to the dissolution of NO₂⁻ species, one of the components of the SEI, as well as O₂ corrosion issues on the Li metal side, thus resulting in unstable cycling of Li–O₂ batteries. Herein, by combining the electrochemical polishing technology with the LiNO₃ reduction chemistry, we construct on a Li metal surface a stable molecularly smooth SEI which possesses a unique multi-layered structure that encapsulates the soluble NO₂⁻ species inside the inner layer. Such an SEI film can not only avoid the negative effects caused by the dissolution of NO₂⁻, but also effectively suppress the dendrite growth on and the O₂ permeation to the Li surface. Consequently, the cycle lives of O₂-saturated symmetric Li cells and Li–O₂ batteries are both improved substantially. Our work offers an effective strategy to protect Li metal anodes in Li–O₂ batteries, and meantime, provides a novel insight into the rational utilization of electrolyte additives.